010.Controller methods and views --控制器方法与视图

Posted 2020-10-03 Meng.NET

索引：

目录索引

Controller methods and views

控制器方法与视图

2017-3-7 9 分钟阅读时长 作者 

By Rick Anderson

We have a good start to the movie app, but the presentation is not ideal.

我们在movie 应用上已经有了一个好的开始，但是表现层不是很理想。

We don\'t want to see the time (12:00:00 AM in the image below) and ReleaseDateshould be two words.

我们不想看到下图中显示的（12:00:00 AM）并且 ReleaseDate 字段应该显示为两个单词。

 

Open the Models/Movie.cs file and add the highlighted lines shown below:

打开 Models/Movie.cs 文件并且添加下面高亮行的代码：

 1 using System;
 2 
 3 using System.Collections.Generic;
 4 
 5 using System.Linq;
 6 
 7 using System.Threading.Tasks;
 8 
 9  
10 
11 namespace MvcMovie.Models
12 
13 {
14 
15     public class Movie
16 
17     {
18 
19         public int ID { get; set; }
20 
21         public string Title { get; set; }
22 
23  
24 
25         [Display(Name = "Release Date")]
26 
27         [DataType(DataType.Date)]
28 
29         public DateTime ReleaseDate { get; set; }
30 
31         public string Genre { get; set; }
32 
33         public decimal Price { get; set; }
34 
35     }
36 
37 }

C# code

Right click on a red squiggly line > Quick Actions and Refactorings.

在红波浪线上右击，选择 Quick Actions and Refactorings.

Tap using System.ComponentModel.DataAnnotations;

点击 using System.ComponentModel.DataAnnotations

 

Visual studio adds using System.ComponentModel.DataAnnotations;.

VS将自动添加 using System.ComponentModel.DataAnnotations 。

Let\'s remove the using statements that are not needed.

让移除不需要的 using 语句 。

They show up by default in a light grey font. Right click anywhere in the Movie.cs file > Remove and Sort Usings.

他们默认以灰色字体显示。右击 Movie.cs 文件的任何地方，选择 Remove and Sort Usings 。

 

The updated code:

更新后的代码如下：

 1 using System;
 2 
 3 using System.ComponentModel.DataAnnotations;
 4 
 5  
 6 
 7 namespace MvcMovie.Models
 8 
 9 {
10 
11     public class Movie
12 
13     {
14 
15         public int ID { get; set; }
16 
17         public string Title { get; set; }
18 
19  
20 
21         [Display(Name = "Release Date")]
22 
23         [DataType(DataType.Date)]
24 
25         public DateTime ReleaseDate { get; set; }
26 
27         public string Genre { get; set; }
28 
29         public decimal Price { get; set; }
30 
31     }
32 
33 }

C# code

We\'ll cover DataAnnotations in the next tutorial.

我们将在接下来的教程中讲解数据注解特性。

The Display attribute specifies what to display for the name of a field (in this case "Release Date" instead of "ReleaseDate").

Display 特性特别的指定了该字段在界面显示时所要显示的名字（用 Release Date 代替了 ReleaseDate）。

The DataType attribute specifies the type of the data (Date), so the time information stored in the field is not displayed.

DataType 特性特别指定了数据的显示类型（日期），因此字段里面存储的时间信息就不再显示了。

Browse to the Movies controller and hold the mouse pointer over an Edit link to see the target URL.

导航到 Movies 地址，在页面上将鼠标放到 Edit 链接上，并查看目标URL.

 

The Edit, Details, and Delete links are generated by the MVC Core Anchor Tag Helper in the Views/Movies/Index.cshtml file.

在Views/Movies/Index.cshtml  文件中的 Edit, Details和 Delete 链接由mvc链接帮助类自动生成的。

1         <a asp-action="Edit" asp-route-id="@item.ID">Edit</a> |
2 
3         <a asp-action="Details" asp-route-id="@item.ID">Details</a> |
4 
5         <a asp-action="Delete" asp-route-id="@item.ID">Delete</a>
6 
7     </td>
8 
9 </tr>

HTML Code

Tag Helpers enable server-side code to participate in creating and rendering HTML elements in Razor files.

Tag Helpers 是在服务端参与产生与渲染HTML的。

In the code above,

在上面的代码中，

the AnchorTagHelperdynamically generates the HTML href attribute value from the controller action method and route id.

AnchorTagHelper 动态的生成了html中的href 特征属性的值 （控制器方法与方法的id参数）。

You use View Source from your favorite browser or use the developer tools to examine the generated markup.

你可以使用浏览器的 View Source 或开发工具查看 自动生成的 html 标记。

A portion of the generated HTML is shown below:

部分html如下所示：

1  <td>
2 
3     <a href = "/Movies/Edit/4" > Edit </ a > |
4 
5     < a href="/Movies/Details/4">Details</a> |
6 
7     <a href = "/Movies/Delete/4" > Delete </ a >
8 
9 </ td >

HTML Code

Recall the format for routing set in the Startup.cs file:

回想 Startup.cs 文件中的路由设置，如下：

 1 app.UseMvc(routes =>
 2 
 3 {
 4 
 5     routes.MapRoute(
 6 
 7         name: "default",
 8 
 9         template: "{controller=Home}/{action=Index}/{id?}");
10 
11 });

C# code

ASP.NET Core translates http://localhost:1234/Movies/Edit/4 into a request to the Edit action method of the Movies controller with the parameter Id of 4. (Controller methods are also known as action methods.)

Asp.net core 翻译 http://localhost:1234/Movies/Edit/4 地址为对 Movies 控制器中方法Edit 的请求，并且参数为4.

Tag Helpers are one of the most popular new features in ASP.NET Core.

Tag Helpers 是asp.net core 中最受欢迎的特点之一。

See Additional resources for more information.

查看 Additional resources 了解更多信息。

Open the Movies controller and examine the two Edit action methods.

打开 Movies  控制器，查看两个 Edit  方法的代码。

The following code shows the HTTP GET Edit method, which fetches the movie and populates the edit form generated by the Edit.cshtml Razor file.

下面的代码是 HTTP GET Edit 方法，他读取了movie数据并填充了由 Edit.cshtml 文件生成的编辑表单。

 1 // GET: Movies/Edit/5
 2 
 3 public async Task<IActionResult> Edit(int? id)
 4 
 5 {
 6 
 7     if (id == null)
 8 
 9     {
10 
11         return NotFound();
12 
13     }
14 
15  
16 
17     var movie = await _context.Movie.SingleOrDefaultAsync(m => m.ID == id);
18 
19     if (movie == null)
20 
21     {
22 
23         return NotFound();
24 
25     }
26 
27     return View(movie);
28 
29 }

C# code

The following code shows the HTTP POST Edit method, which processes the posted movie values:

下面的代码展示了 HTTP POST Edit 方法，他处理了post请求过来的movie数据：

 1 // POST: Movies/Edit/5
 2 
 3 // To protect from overposting attacks, please enable the specific properties you want to bind to, for
 4 
 5 // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
 6 
 7 [HttpPost]
 8 
 9 [ValidateAntiForgeryToken]
10 
11 public async Task<IActionResult> Edit(int id, [Bind("ID,Title,ReleaseDate,Genre,Price")] Movie movie)
12 
13 {
14 
15     if (id != movie.ID)
16 
17     {
18 
19         return NotFound();
20 
21     }
22 
23  
24 
25     if (ModelState.IsValid)
26 
27     {
28 
29         try
30 
31         {
32 
33             _context.Update(movie);
34 
35             await _context.SaveChangesAsync();
36 
37         }
38 
39         catch (DbUpdateConcurrencyException)
40 
41         {
42 
43             if (!MovieExists(movie.ID))
44 
45             {
46 
47                 return NotFound();
48 
49             }
50 
51             else
52 
53             {
54 
55                 throw;
56 
57             }
58 
59         }
60 
61         return RedirectToAction("Index");
62 
63     }
64 
65     return View(movie);
66 
67 }

C# code

The [Bind] attribute is one way to protect against over-posting.

[Bind] 特性标记是一种post攻击防护方式。

You should only include properties in the [Bind] attribute that you want to change.

你应当只做 [Bind] 特征类中包含的字段的变更。

See Protect your controller from over-posting for more information. 

查看 Protect your controller from over-posting 以获得更多信息。

ViewModels provide an alternative approach to prevent over-posting.

ViewModels 提供一种预防 over-posting 攻击的方式。

Notice the second Edit action method is preceded by the [HttpPost] attribute.

注意第二个 Edit 方法被 [HttpPost] 特征类修饰。

 1 // POST: Movies/Edit/5
 2 
 3 // To protect from overposting attacks, please enable the specific properties you want to bind to, for
 4 
 5 // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
 6 
 7 [HttpPost]
 8 
 9 [ValidateAntiForgeryToken]
10 
11 public async Task<IActionResult> Edit(int id, [Bind("ID,Title,ReleaseDate,Genre,Price")] Movie movie)
12 
13 {
14 
15     if (id != movie.ID)
16 
17     {
18 
19         return NotFound();
20 
21     }
22 
23  
24 
25     if (ModelState.IsValid)
26 
27     {
28 
29         try
30 
31         {
32 
33             _context.Update(movie);
34 
35             await _context.SaveChangesAsync();
36 
37         }
38 
39         catch (DbUpdateConcurrencyException)
40 
41         {
42 
43             if (!MovieExists(movie.ID))
44 
45             {
46 
47                 return NotFound();
48 
49             }
50 
51             else
52 
53             {
54 
55                 throw;
56 
57             }
58 
59         }
60 
61         return RedirectToAction("Index");
62 
63     }
64 
65     return View(movie);
66 
67 }

C# code

The HttpPost attribute specifies that this Edit method can be invoked only for POST requests.

HttpPost 标记特别指定了 Edit 方法只能被 POST 请求调用。

You could apply the [HttpGet] attribute to the first edit method, but that\'s not necessary because [HttpGet] is the default.

你可以在第一个 edit 方法上使用 [HttpGet] 特征类，单他不是必须的，因为方法默认是 [HttpGet] 请求的。

The ValidateAntiForgeryToken attribute is used to prevent forgery of a requestand is paired up with an anti-forgery token generated in the edit view file (Views/Movies/Edit.cshtml).

ValidateAntiForgeryToken 标记类使用了预防伪造请求，并与 edit 视图生成的反伪造令牌是配对的。

The edit view file generates the anti-forgery token with the Form Tag Helper.

edit 视图生成的anti-forgery 令牌是通过 Form Tag Helper 生成的。

1 <form asp-action="Edit">

HTML Code

The Form Tag Helper generates a hidden anti-forgery token that must match the [ValidateAntiForgeryToken] generated anti-forgery token in the Edit method of the Movies controller.

Form Tag Helper 生成了一个隐藏域的令牌字段，并且他是匹配Movies控制器中Edit 方法上的[ValidateAntiForgeryToken] 标记生成的令牌的。

For more information, see Anti-Request Forgery.

查看  Anti-Request Forgery ，以获得更多信息。

The HttpGet Edit method takes the movie ID parameter, looks up the movie using the Entity Framework SingleOrDefaultAsync method, and returns the selected movie to the Edit view.

HttpGet Edit 方法获取 ID 参数，查看 EF 的 SingleOrDefaultAsync 方法，它会查找并将movie数据返回给 Edit 视图。

If a movie cannot be found, NotFound (HTTP 404) is returned.

如果movie数据没有找到，将返回 NotFound 。

 1 // GET: Movies/Edit/5
 2 
 3 public async Task<IActionResult> Edit(int? id)
 4 
 5 {
 6 
 7     if (id == null)
 8 
 9     {
10 
11         return NotFound();
12 
13     }
14 
15  
16 
17     var movie = await _context.Movie.SingleOrDefaultAsync(m => m.ID == id);
18 
19     if (movie == null)
20 
21     {
22 
23         return NotFound();
24 
25     }
26 
27     return View(movie);
28 
29 }

C# code

When the scaffolding system created the Edit view, it examined the Movie class and created code to render <label> and <input> elements for each property of the class.

当MVC基架系统创建了 Edit 视图，它会自动检查 Movie 类的每个属性，并未每个属性创建HTML元素。

The following example shows the Edit view that was generated by the Visual Studio scaffolding system:

下面的例子展示了VS基架系统自动生成的 Edit 视图：

  1 @model MvcMovie.Models.Movie
  2 
  3  
  4 
  5 @{
  6 
  7     ViewData["Title"] = "Edit";
  8 
  9 }
 10 
 11  
 12 
 13 <h2>Edit</h2>
 14 
 15  
 16 
 17 <form asp-action="Edit">
 18 
 19     <div class="form-horizontal">
 20 
 21         <h4>Movie</h4>
 22 
 23         <hr />
 24 
 25         <div asp-validation-summary="ModelOnly" class="text-danger"></div>
 26 
 27     <input type="hidden" asp-for="ID" />
 28 
 29         <div class="form-group">
 30 
 31             <label asp-for="Title" class="col-md-2 control-label"></label>
 32 
 33             <div class="col-md-10">
 34 
 35                 <input asp-for="Title" class="form-control" />
 36 
 37                 <span asp-validation-for="Title" class="text-danger"></span>
 38 
 39             </div>
 40 
 41         </div>
 42 
 43         <div class="form-group">
 44 
 45             <label asp-for="ReleaseDate" class="col-md-2 control-label"></label>
 46 
 47             <Learning an Optimal Policy: Model-free Methods

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